View Single Post
Old 06-08-2009, 06:11 PM
jibbguy jibbguy is offline
Silver Member
Join Date: Jun 2008
Posts: 987
R'gh, m8ey ;)


While AC "Impedance" can only be calculated, and is a Variable dependent on the Frequency of the signal and many other factors such as material composition and specific design of the components (yet it is still a very "real" phenomena for sure); DC "Resistance" of course can be accurately measured and is generally a Constant (...Except sometimes for "temperature", lol).

So did you mean the "R" of the coils?

But it does not really matter at all what the R of a coil is, as the only interest here is when the AC signal is applied. Any two coils could possibly be of differing DC Resistance; yet can still Resonate at the same F (.. and when coupled with the same value Capacitor)... It depends entirely on how they were made: The number of turns, the distance between turns on the spool, the wire gauge, the wire's metal composition, the core, and of course the phase of the moon lol ).

When we make two coils ourselves, we do it the same way, with the same materials, core, and turn spacing... So the DC "R" can then matter as an indicator.

But i do remember having to hand-match auto-transformers before when working on old oscilloscope power supplies: Even though they looked & Ohm'ed identical (same P/N), they can still be different enough somehow to cause problems in a tightly balanced circuit (ahh, the bad-old days of Analog and continuous supplies.. I used to dream of getting revenge on the engineers lol).

But i fully agree with the rest of your post, and that the Murray stuff is fascinating.

What ever happened to this guy? Does anyone know what is he doing these days?